The v-myc protein, p110, produced by MC29 nonproducer quail cells (Q8) was substantially purified by sequential column chromatography. The most efficient purification was achieved by a sequence of Sephacryl S-400, DEAE-Sephadex, and G-75 columns. Stages of purification were monitored by immunoprecipitation of the p110 with gag and myc antisera. Potassium-adenosine triphosphatase (ATPase) was found to be associated with the p110 throughout the purification. The enzyme activity could not be eliminated by high speed centrifugation or sonication. The purified p110-ATPase showed optimum activity at pH 6.0 and in the absence of Mg++. The p110 did not show any in vitro adenylation activity.